The invention relates to a conveying plant for work pieces to be processed or assembled one after another at different working positions comprising a guide rail extending longitudinally at said working positions, a push-in device arranged at one end of the guide rail and a push-out device at the other end thereof, a conveying rail arranged parallely with and adjacent to the guide rail, a plurality of dogs provided at the conveying rail at equal interspaces, a drive unit operatively connected with the conveying rail and moving the conveying rail along a continuously repeated substantially rectangular moving path consisting of a working stroke in longitudinal direction of the guide rail, a disengaging stroke, a return stroke parallel with the working stroke and a reengaging stroke.
A conveying plant of this kind is known from West German patent application No. 21 64 087. It is true that no push-in and push-out devices are shown there, however, such devices belong to automatic conveying plants.
Another conveying plant is known from West German patent application No. 27 56 096. In this known art a pair of conveying rails are used having a plurality of recesses facing one another respectively such said each pair of recesses of both conveying rails forms a pair of clamping jaws for a specially shaped article. Both rails are mounted for common longitudinal motions and oppositely directed transverse motions. In contrast to the art mentioned before no stationary guide rails are present. The articles to be processed must be held by intermediate grippers or the like when the rails move away from one another.
In modern flexible fabrication systems different work pieces are processed and assembled in one and the same processing machine for example a bending machine. Both that known conveying machines need specially shaped conveying rails which are adapted to the special type of work pieces. In order to transport another kind of work piece the conveying rails must be replaced by rails of different shape. A further disadvantage of the known conveying plants must be seen in that additional holding means are required to hold the work pieces during the processing operations as in the aformentioned German publication No. 21 64 087 or after that processing operations when the rails open the clamping areas as in the publication No. 27 56 096.
Indeed additional gripping tools could be mounted at each working station however, those tools must be exchanged when different shaped work pieces are to be handled. With the guiding rails in the German publication No. 21 64 087 no clamping function can be achieved. The work pieces merely rest on that guiding rail and any lateral supporting surfaces are missed. If guiding rails would be used having a holding function for the special work pieces, that guiding rails would have be exchanged too when work pieces of different shapes and sizes are to be processed.